1. Technical Field
The present invention relates to a V-cutter used to manufacture light guide panels for backlight units for liquid crystal displays (LCD), and more particularly, to a V-cutter designed to form a plurality of V-shaped grooves in the light guide panel at a specified interval with two reciprocating motions.
2. Background Art
An LCD (liquid crystal display) unit, such as may be used in a flat panel computer screen, is not self-illuminating, and therefore requires a separate backlight unit with a light source behind the LCD unit.
Because a large investment in the LCD industry has been made in Japan, Korea and Taiwan, demand for the LCD unit, backlight unit, and other related parts is increasing accordingly.
Recently, LCD units have become smaller and lighter. Accordingly, backlight units for the new LCD units have become thinner and lighter through the use of a side light configuration.
In a backlight unit with a side light configuration, the emitted light by a light source to the side of the light guide panel is dispersed to have a uniform luminance across the light guide panel, so that a regular pattern is formed on the bottom of the light guide panel.
Since the light source for emitting the light is disposed on the side of the light guide panel, the pattern with a wider interval is disposed at the area adjacent to the light source and the pattern with a narrower interval is disposed at the area far from the light source, in order to keep the luminance uniform across the surface of the light guide panel.
The pattern on the bottom of the light guide panel used to disperse the light from the side-mounted light source may be, for example, a known groove pattern type for TFT-LCD monitor or a print pattern type for a notebook computer screen.
FIG. 1 is a longitudinal sectional view of one example of a backlight unit with light guide panels disposed in a groove pattern in which the upper portion is a plane of the light guide panel on which the liquid display elements are disposed, and the lower portion is a bottom of the light guide panel.
On a side of the light guide panel 1 having a transmission material, a light source 2 for illuminating the LCD unit is disposed. The light source may take the form of a cool cathode fluorescent lamp (CCFL). At the bottom of the light guide panel a plurality of V-shaped grooves 3, or grooves 3, are formed. The V-shaped grooves 3 serve to uniformly disperse the light emitted by the light source 2. A reflecting seat 4 constructed of a reflective material, such as PET, is attached thereon.
The grooves 3 formed on the bottom on the light guide panel 1 disperse the emitted light from the light source 2 across the upper surface of the light guide panel. The grooves 3 are separated by a wider interval in vicinity of the light source 2 because the light against the nearer grooves 3 has a comparatively high luminance. The grooves 3 further from the light source 2 are spaced apart by a narrower interval so that the luminance can be uniformly maintained on the plane of the light guide panel 1.
In the backlight unit, light from the light source does not simply travel straight, but is refracted at a predetermined angle, as depicted by the arrows in FIG. 1, to disperse on the inner surface of the light guide panel. The refracted light then provides backlighting for the LCD unit disposed on the upper surface of the light guide panel.
The light emitted by the light source 2 is uniformly refracted by V-shaped grooves 3 formed on the plane of the light guide panel 1 by a device called a xe2x80x9cV-cutterxe2x80x9d.
Conventionally, a V-cutter has a lift piece disposed on slider that moves horizontally (along the X-axis) along a guide rail. A controller such as a hydraulic or mechanical cylinder or a step motor may vertically actuate the lift piece. A pin for forming the V-shaped grooves 3 on the light guide panel may be affixed to the bottom surface of the lift piece. The light guide panel is typically fixtured on a table configured to move a single step (one pitch) perpendicular to the direction of motion of the slider after the formation of each groove, so that the next groove can be made at the proper location.
In operation, the slider moves along the guide rail (in the direction of the X-axis) and the lift piece is lowered (in the direction of the Z-axis) to the bottom dead center position by the controller. The slider and lift piece then return to their initial positions to complete formation of one V-shaped groove in the light guide panel.
After formation of the first of the V-shaped grooves 3, the table moves indexes the light guide panel to a different position with respect to the lift piece to form another of the grooves 3 at a pitch, or displacement from the first groove. This process repeats until all of the V-shaped grooves 3 have been formed with the proper pitch.
The conventional method is disadvantageous because the grooves 3 must be formed one-by-one on the light guide panel. Considerable machine and operator time is required. As a result, the lead time and manufacturing cost of the backlight manufacturing process is somewhat high.
Additionally, with the reciprocal movement of the slider along the guide rail, the table must be indexed by 1 pitch to form the parallel V-shaped grooves 3 on the light guide panel. This indexing typically requires that the table be moved in a direction 90 degrees from the horizontal motion of the slider. This indexing requires additional time for the formation of each groove. As a result, still more time is required to complete formation of the V-shaped grooves 3 on the light guide panel.
Furthermore, the conventional technique utilizes only a single pin to manufacture all of the V-shaped grooves 3. With such heavy use, it is inevitable for the pin to wear out after a comparatively short lifetime. Thus, frequent maintenance of the V-cutter is required, and more light guide panels may need to be scrapped or reworked due to processing with worn-out pins.
The present invention provides a system and method for solving the problems presented by known V-cutters. One object of the invention is to simultaneously form V-shaped grooves through the use of a plurality of pins corresponding to the grooves on the light guide panel in a simple, two-time operation.
In order to achieve the objects of the invention, an enhanced V-cutter is provided for manufacturing light guide panels for LCD units. According to one aspect of the present invention, the V-cutter may have a two pin kits, each of which has a plurality of pins separated by the proper spacing to form V-shaped grooves with a predetermined interval on the light guide panel. The light guide panel may be fixtured on a table configured to move in a Y-axis direction. One of the pin kits may be affixed to a Z-axis lift piece, while the other is affixed to a W-axis lift piece. A Z-axis controller and a W-axis controller may vertically actuate the lift pieces. The Z-axis lift piece and the W-axis lift piece may be disposed on an X-axis slider configured to move in an X-axis direction. Thus, the table and X-axis slider can be successively actuated only one time each to form perpendicular V-shaped grooves on the light guide panel.
According to another aspect of the present invention, the Z-axis lift piece may be affixed to a body or a fixed frame of the V-cutter instead of the X-axis slider.
According to further aspect of the present invention, the table may be attached to an X-axis slider, and the Z-axis and W-axis lift pieces may both be stationary. The table may then move in both X-axis and Y-axis directions so that the pins can form the perpendicular V-shaped grooves.
According to yet another aspect of the present invention, the table may be stationary, and an X-axis slider may be affixed to a moving frame configured to move in the Y-direction. The W-axis lift piece and the Z-axis lift piece may both be attached to the X-axis slider, so that the perpendicular V-shaped grooves can be formed through motion of the X-axis slider and the moving frame.
In order to manufacture larger light guide panels, dual W-axis or Z-axis lift pieces may be provided and arranged side-by-side. Each lift piece may have a pin kit with a plurality of pins. In order to fabricate a wide row of V-shaped grooves, one lift piece may be lowered to create a series of V-shaped grooves, and then the other lift piece may be indexed into position to continue the row of V-shaped grooves without any abnormal spacing between the V-shaped grooves created by the two lift pieces. Dual lift pieces could be used for the Z-axis or W-axis lift pieces, and may be incorporated into any of the V-cutter configurations described above.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.